Stop Security Center from whinging

Security Center, which was introduced with Service Pack 2 and is still very much present in Service Pack 3, likes to tell you all the time that your system is insecure, especially if you've got Automatic Updates turned off, or a firewall or antivirus running that it doesn't recognise. To silence its complaints:

Go to Start > Settings > Control Panel > Security Center
On the left-hand side of the application click the link that says Change the way Security Center alerts me
Uncheck the item(s) causing you grief — either Firewall, Automatic Updates, Virus Protection — then click OK